Until recently, a point-to-point (from source to recipient) communication in the Internet, computer networks and data networks was definitely the prevailing way. Current applications, multimedia in particular, such as video conferences or television and radio broadcast via networks, however often transport data stream from a single source to multiple recipients. In order to ensure that transmission capacities for this purpose are still sufficient, or that their exploitation is economic, data stream is replicated, i.e. copied, and split not at the source but in a network point closer to recipients. Data stream replication so far is carried out by transmission devices—switches or routers, which transform optical signal to electronic signal, store it by parts, e.g. packets, into the memory of the switch, replicate it and re-transform each created copy from electronic form back to optical signal. This rather demanding action imposes increased load for switch or router, especially when implemented only as an additional software feature without special hardware support. Replication method mentioned above typically results in repeated gradual copying of input data into relevant output queues. These data are processed by the switch or router simultaneously along with processing other transmissions. This fact then causes non-deterministic delay introduced in data stream, so-called jitter, and may result in random data losses. These effects in particular may rather negatively affect quality of transmitted, especially multimedia, content, which in order to ensure acceptable perception by human senses demands wide bandwidth, low loss rate and low jitter. Jitter is represented by undesired and typically also non-deterministic delay variations and other signal characteristics and in connection with multimedia transmissions these may result for instance in jerky or broken image or sound.
On the contrary, all-optical replication of signals, given by its principle, takes place in real time and the output data streams are exact copies of input data stream. Therefore, no non-deterministic delays and data losses may occur. Although products of photonic industry suitable as components for all-optical replication solutions exist for many years already, no devices applicable for large research networks and subsequently for large commercial networks have been available so far. Existing devices addressing this issue show significant limitations, such as limited number of splitting, narrow band of signal wavelengths—typically C-band only, missing functional features for direct use as a device for multicast of optical signal in the Internet and other networks.